Multivibrator circuit



July 15, 1952 Filed May 25, 1950 ll llllllH 4lllllllll'r g 7 P0710774: 471M050; zwim Pam/m4 mam x0; 705520 WILLIAM AMILLER Ihmcntor (Elm-mg negative bias source.

Patented July 15, 1952 MULTIVIBRATOR critoUrr William A. Miller, Port J efferson, N. Y., assignor to Radio Corporation of of Delaware Application May 25, 1950, S

America, a corporation erial-No. I

6 Claims. (01. 250-36) This invention relates to oscillators. More particularly the present invention is an improvev ment in relaxation oscillators of the type known as multivibrators. I

In many applications of multivibrators in sweep circuits .or as pulsers, it is desirable that the output voltage or pulses from the multivibrator be clamped or have one extremity of the waveform always return to the same reference potential. D. C. restorers or clamping circuits are employed to perform this function.

.Furthermore, much, additional, complex circuitryis required in the event it is desired to make the reference potential, to which a waveform is clamped, a variable one.

Serial No. 164,078, filed May 25, 1950, there is described and claimed a. trigger circuit which provides an output which is automatically clamped to a reference potential.

It is an object of the present invention to provide an improved relaxation oscillator having an output which is automatically clamped to a reference potential.

' It is another object of the present invention to provide an improved relaxation oscillator having an output which is automatically clamped to a reference potential which is adjustable.

These andfurther objects of the present invvention are achieved by providing a two-tube multivibrator having cross-connectedgrids and anodes wherein a first one of the tubes hasits anode connected to the B-+ power supply through a load resistor and its cathode and grid to ground potential and a second one of the tubes has its anode connected to ground potential through aload resistor and its cathode-and-grid to a This provides, at the .Figure 1 is a circuit diagram of an embodiment of the invention,

In a copending application for an Electronic Locking Circuit,

circuit shown in Figure -1,

Figure-2 is a graphical representation of r the wave-shapes of the output available from the Figure 3 is a circuit diagram of a modificati n of the embodimentof theinvention shown in Figure 1, and- V I 1 Figure 4 is a graphical representation of the wave-shapesv of the output available from one of the tube anodes in the circuit shownln Figure 3.

Referring now to Figure 1, a first electron discharge tube [0 has an anode l 2;=connected to the grid 24 of a second electron discharge tube 20 through a condenser l8. The grid ld.

of the first electron discharge. tube 10 isconnected to the anode 22 of the second tube 20 through a condenser 28. A grid leak resistor 30 is connected between the cathode l6. and grid M of the first tube I0. Another grid leak resistor 32 is connected between cathode 26 and grid 24 of the second tube 20.

A source of operating potential 34 is provided having a positive terminal 36 which is positive with reference to ground or a point of reference potential 38, and a negative terminal 49 which is negative with reference to ground 38. A load resistor 421s connected between the anode [2 of the first tube and the positive terminal 36. The cathode I6,,of the first tube is connected to the point of reference potential, 38. A load resistor 44 is connected between the anode of the second tube and the point of reference potential 38. The cathode 26 of the second tube is connected to the negative terminal 40.

The operation of the circuit is typically that of a free-running multivibrator. Current conduction is transferred from one tube to the other alternately. The frequency of the transfer, as of the oscillation, is principally determined by the values of the coupling condensers and grid leak resistors, and .to a lesser extent by the values of the anode load resistors and the value of the source of operating potential. An explanation of the operation of a multivibr'ator may be found in Theory and Applications of Electron Tubes by Reich, pages 362 to 365, published by McGraw-Hill Book Company.

In the circuit shown in Figure 1, however, in

the voltage output at the anode 22 of the second tube 20 is also substantially rectangular and varies from ground potential, when the tube is not conducting, to a negative value, when the tube is conducting. The amount that the second tube amide i'willggo negative depends upon the I amountof" current drawn bfthetube and the Therefore, the output from the anode of the second tube value of the load resistor 44.

clamped to ground or reference potential,

from the anode of the second tube. Figure 3 is a oircuitdiagram of a modification of Figure-'1 l'Simi-lar functioning parts of Figure -3 are identified -by 'similar reference numerals.

The modification consistsr of' a #potentio-meter -46having its fixed resistance 48 connected across-the power s'upplytd in a mannerto include values of potential which are positive referred-to the point of reference potential and negativerefer-red' tothe point of reference-potential. "This nlay 'be done by tapping the source, as shown, using supplementary dropping "*resi'stors, or in any other manner which is known -to 'the art.

The arm of the potentiometer 0,

' wliich is in slidable contact with 'i'tS" fiX8d':IeSlStance,-- is connected to the anode load resistor 44 of thesecond 'tube'20. -A condenser 52 is con- 'ne'eted between the potentiometer I slidable arm 5B -'and-'-the point of reference potential 33 in "orderto -maintain a constant AJC; load on the secondtube.

i --Movement of the-potentiometerslidable armitll permits application'of potentials from a positive value through zero'to a: negative value. :The

effect; of these" variations on the output I from 'the' second tube anode is shown in Figure 4.

'Pulse A represents a typical output pulse when the slider a'rm 59 isat theground pot'ential point. Pulse B'represents a typical output pulse when the 'slider arm applies a voltage which is-below ground and pulse C is representative 'of'a typical output. pulse when the slider arm appliesa voltageabove-ground. The range over- "which this va-riation may be carried out is determined ma-inly by the ameunt of voltage swing of the anode 12 01" the firsttube l0. Thus the reference -or clamping 1 level of the output at the second-tubeano'de may be controlled as de- -s-ired*by adjusting the potentiometer. Although the subject multivibrator -is described using triodes, mul-tigrid tubes are equally Y effective,

f i rom the foregoing description it; will; be read- "'n'i'ent and modification iofthe present invention beyaiied'as'desired. "Although a singleembodihas been shown and'desciibed'it should l: eap- Iparentthat many changes'm'ay be made in' the 'p'a 'rticular embodiment herein disclosed, and that inany othe-r embodiments are'possible, all within "the spirit and scope of-the present invention.

lt is ,desired,l-therefore, that the foregoing'descriptionshall be taken -as illustrative andnot .aslimiting. g V

, What is'claim'ed is: v r 1: A- relaxation o cilla or ompri n fi en No D. C. restoration 4 anode, cathode and grid electrodes, the grid of said first tube being coupled to the anode of said second tube, the grid of said second tube being coupled to the anode of said first tube, a grid 5 leak resistor for each of said tubes connected between the grid 'andcathode Roi each tube, a "first anode loadimpedan'ce' having one end connected to the anode of said first tube, a second anode load impedance having one end connected tc'ithe anode of said second tube, a point of refview of the connection to ground potential, the V anode 22 of the second tube' ZD -may-beconnected directly to succeeding apparatus without the usual coupling condenser being required to block l out anode D. C. potential.

or clamping is required for an output taken erence potential, said first tube cathode being *connected-to'said point of reference potential, "means 'toiapply a potential which is positive with respect'to 'said'reference potential point to the 5 other. end of said first anode load impedance,

means to apply a potential which is negative with respect to said reference potential point to said second tube cathode, means to apply a potential of-sa-id potential from values-above to values' below said reference potential point.

' 2; A relaxation oscillator circuit-comprising first and second electron discharge tubes *each 25 "having anode, cathode and -grid electrodesthe grid otsaid' first' tube being-coupled to the anode "of-saidsecond tube, the-grid of said second tube being coupled to theanode ofsaid-first tube 'a grid leak resistor for 'eachof'said tube-s oonnected'between'thegrid and cathode of each tube, -afirst anode' lead impedance having" one end connected to said first tube anode, a second anode load impedance having one end connected tosaidsecond tube anode, a point of fixed poten- 5 tial, the other end of saidsecond anode-load impedanceandsaid first tube cathode being' connected to said point of fixed potential, means to apply a potential whichis positive 'with're spect to said point-of fixed potential to-said other 40 end of said first anode load impedance, and

*means-to apply a potential which is negative with respect to said point of-fixed' potential 'to said cathode of saidsecond tube.

' 3. A *relaxa-tion' oscillator circuit comprising firs't and second electron discharge tubes each having anode, 'cathodeand grid electrodes, the grid of said first tube being coupled to the anode of saidsecond tube, the grid of said second tube being coupled to the'anode of said first tube, a grid leak resistor foreach of said tubes connected between the grid and cathode of eachtube. a first-anode load impedance having one end connectedtostheanode of said first tube, a second anode loadimpedance having one-end connected 5 to theanode of said second tube, a point of reference potential; said first tube cathodebeing connected to said point of reference potentiaLxmeans to-apply a' potential which islpositive withsrespect to said reference potential point to the other end 7 of said first anodeload impedance, means to apply a potential which is negativewith respect to said reference potential point to'said-se'cond tube ca thode, a potentiometer including arfixed ,impedance and-an arm slidably in contactwith said imp,edance, said slidable arm being connected to the other end of-said -second anode load 1mpedance,;means to. apply a potential-whichis v:pos1t1vewith respect to said-reference:potential point-to one end-of said potentiometerfixed impedance, and means to apply a potential which ,is negativewith'respect to said reference potential point to theotherend of said potentiometer'fixed impedance.

, 4. Arelaxation oscillator circuit as recited in Second t n discharge tubes each having 7 claim shaving in addition a condenserconnected 7 between said potentiometer slidable arm and said point of fixed potential.

5. A relaxation oscillator comprising first and second electron discharge tubes, each tube having an anode, cathode and grid electrode, each tube tial, a positive terminal which is more positive than said point of reference potential and a negative terminal which is more negative than said point of reference potential, the other end of said load resistor of said first tube being connected to said positive terminal, said first tube cathode and the other end of said load resistor of said second tube being connected to said point of reference potential, and said second tube cathode being connected to said negative terminal.

7 6. A relaxation oscillator comprising first and second electron discharge tubes, each tube having an anode, cathode and grid electrode, each tube having a separate grid leak resistor connected between said tube grid and cathode and each tube having a separate load resistor with one end connected to said tube anode, the grid of said first tube being capacitively coupled to the anode of said second tube, the grid of said second tube being capacitively coupled to the anode of said first tube, and a source of direct current potential, said source including a point of reference potential, a positive terminal which is more positive than said point of reference potential and a negative terminal which is morenegative than said point of reference potential, the other end of said load resistor of said first tube being connected to said positive terminal, said first tube cathode being connected to said point of reference potential and said second tube cathode being connected to said negative terminal, a potentiometer including a fixed resistance and anarm slidably in contact with said fixed resistance, means to couple said potentiometer fixed resistance between said positive and negative terminals to provide a range of potentials along said fixed resistance including said reference potential, the other end of said second tube load resistor being connected to said potentiometer slidable arm and a condenser connected between said second tube load resistor other end and said point of reference potential.

WILLIAM A. MILLER.

REFERENCES CITED UNITED STATES PATENTS Name Date Canfora May 4, 1948 Number 

